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Kinh Doanh - Tiếp Thị - Nông - Lâm - Ngư - Nông - Lâm - Ngư Final report Project Improving the sustainability of rice- shrimp farming systems in the Mekong Delta, Vietnam project number SMCN2010083 date published 10 August 2020 prepared by AProfessor Jesmond Sammut, UNSW Dr Nguyen Van Sang (RIA2) co-authors contributors collaborators Dr. Nguyen Van Hao (RIA2), Professor Le Quang Tri (CTU), Professor Michele Burford (Griffith University), Dr Jason Condon (CSU) Dr Chau Minh Khoi (CTU), Dr Ben Stewart-Koster (Griffith University), Dr Catherine Leigh (Griffith University RMIT), Dr Cao Van Phung (CLRRI), Nguyen Kim Thu (CLRRI), Dr Duong Minh Vien (CTU), Nguyen Van Sinh (CTU), Le Huu Hiep (RIA2), Luu Duc Dien (RIA2, Griffith University), Le Van Truc (RIA2), Dang Duy Minh (CTU), Dr Dang Kieu Nhan (CTU), Nguyen Cong Thanh (RIA2), Dr. Nguyen Thi Ngoc Tinh (RIA2), Vo Bich Xoan (RIA2), Ngo Thi Ngoc Thuy (RIA2), Nguyen Minh Duong (RIA2), La Thuy An (RIA2), Doan Thi Truc Linh (CTU), Ho Nguyen Hoang Phuc, Nguyen Van Trong (RIA2), Doan Van Bay (RIA2), Nguyen Van Qui (CTU) and Hoang Thi Thuy Tien (RIA2). approved by Dr James Quilty final report number ISBN published by ACIAR GPO Box 1571 Canberra ACT 2601 Australia 978-1-922635-25-9 FR2021-062 This publication is published by ACIAR ABN 34 864 955 427. Care is taken to ensure the accuracy of the information contained in this publication. However ACIAR cannot accept responsibility for the accuracy or completeness of the information or opinions contained in the publication. You should make your own enquiries before making decisions concerning your interests. Australian Centre for International Agricultural Research (ACIAR) 2021 - This work is copyright. Apart from any use as permitted under the Copyright Act 1968 , no part may be reproduced by any process without prior written permission from ACIAR, GPO Box 1571, Canberra ACT 2601, Australia, aciaraciar.gov.au. Final report: Improving the sustainability of rice-shrimp farming systems in the Mekong Delta, Vietnam Page iii Contents 1 Acknowledgments .................................................................................... 5 2 Executive summary .................................................................................. 6 3 Background............................................................................................... 7 4 Objectives ................................................................................................. 9 5 Methodology ........................................................................................... 10 6 Achievements against activities and outputsmilestones .................. 19 7 Key results and discussion ................................................................... 28 7.1 Bayesian Belief Networks................................................................................................. 28 7.2 Shrimp growth models...................................................................................................... 31 7.3 Shrimp feeding trials 2019................................................................................................ 32 7.4 Shrimp better management practices .............................................................................. 34 7.5 Risk Factors relating to rice .............................................................................................. 34 7.6 Soil Management to decrease salinity.............................................................................. 36 7.7 Rice farming options to mitigate effects of salinity ........................................................... 38 7.8 Production efficiencies ..................................................................................................... 39 7.9 Agronomic recommendations to farmersadvisors: .......................................................... 41 7.10 Research recommendations: ........................................................................................... 42 7.11 Socio-economic results .................................................................................................... 43 8 Impacts .................................................................................................... 49 8.1 Scientific impacts – now and in 5 years ........................................................................... 49 8.2 Capacity impacts – now and in 5 years ............................................................................ 50 9 Community impacts – now and in 5 years ........................................... 52 9.1 Economic impacts ............................................................................................................ 52 9.2 Social impacts .................................................................................................................. 52 9.3 Environmental impacts ..................................................................................................... 52 10 Communication and dissemination activities ..................................... 54 11. Conclusions and recommendations ....................................................... 58 10.1 Conclusions ...................................................................................................................... 58 10.2 Recommendations ........................................................................................................... 59 Final report: Improving the sustainability of rice-shrimp farming systems in the Mekong Delta, Vietnam Page iv 11 References .............................................................................................. 60 12 Appendixes ............................................................................................. 61 12.1 Appendix 1: Publications list (see Excel file) .................................................................... 61 Final report: Improving the sustainability of rice-shrimp farming systems in the Mekong Delta, Vietnam Page 5 1 Acknowledgments The project team thanks Dr Gamini Keerthisinghe and Dr Robert Edis (former Research Program Managers of the ACIAR Soil Management Crop Nutrition Research Program), Dr James Quilty (current Research Program Manager of the ACIAR Soil and Land Management Research Program), Dr Chris Barlow (former Research Program Manager of the ACIAR Fisheries Program) and Dr Ann Fleming (Research Program Manager of the ACIAR Fisheries Research Program) for their support and guidance. This project was conceptualised by Drs Keerthisinghe, Barlow (ACIAR) and Nguyen Van Hao (RIA2) who brought together the research agencies and invested in the project design and overall project monitoring and evaluation. A project of this size, and with multiple agencies across two countries, was made easier to manage with the help of Maree Livermore, Rachel Roberts, Sarah Bourne and Rachel McGrath from ACIAR, Nguyen Van Tien from RIA2, and Jenny Saunders and Sharon Ryall from UNSW. We are grateful to Nguyen Thi Thanh An, Nguyen Thi Lan Phuong and Phạm Bích Thuỷ from the ACIAR Country Office in Hanoi for project support, facilitating engagement with stakeholders, promoting project activities in Vietnam, and arranging local project reviewers. We thank ACIAR for funding this project and facilitating the research partnerships during the project design stage. ACIAR also funded a John Allwright Fellowship for Dr Luu Duc Dien (RIA2) who completed a PhD at Griffith University on a separate project topic that contributed significantly to this project. We are grateful to Stephen Faggotter (Griffith University) for field assistance and project team training, and Graeme Curwen for GIS support. Nguyen Minh Duong and La Thuy An (RIA2) are thanked for field work support. We are grateful to the farmers at Hoa My and Tan Bang communes for providing access to their farms for field trials, providing meals and field support, and participating in socio-economic surveys and feedback sessions that helped focus our research activities. We acknowledge the tremendous support of the Department of Agriculture and Rural Development (DARD) and its field staff who facilitated engagement with farmers and assisted the team with training and other dissemination activities. We thank Angelia Liu (UNSW) for helping to compile materials for this final report. The project was led by AProfessor Jesmond Sammut, UNSW, Dr Nguyen Van Hao and Dr Nguyen Van Sang (RIA2) with support from Professor Michele Burford (Griffith University), Professor Le Quang Tri (CTU), Dr Chau Minh Khoi (CTU), Dr Cao Van Phung and Ms Nguyen Kim Thu (CLRRI), and Dr Jason Condon (CSU). The project leaders thank the project team from UNSW, RIA2, CSU, Griffith University, CTU and CLRRI for their significant role in developing and implementing the project. CTU, RIA2 and CLRRI are thanked for supporting six Australian interns from UNSW and honours students from UNSW, Griffith and CSU. Final report: Improving the sustainability of rice-shrimp farming systems in the Mekong Delta, Vietnam Page 6 2 Executive summary Farming rice and shrimp in an integrated pond system is practiced widely in the Mekong Delta where dry season soil and water salinity is too high to continue with rice monoculture. These integrated systems involve farming rice in the wet season when soil and water salinity is normally negligible, and shrimp in the dry season when soil and water salinities exceed the tolerance of rice. In recent decades, these systems have been subjected to rising salinity due to climate variability and reduced freshwater flows into the Mekong Delta from upstream river regulation for dams and abstraction of water for other land uses. Consequently, wet season salinity is increasing and creating sub-optimal conditions for rice; dry season salinity is also becoming sub-optimal for shrimp at some locations due to hypersalinity. Nevertheless, these rice-shrimp systems, when risks are managed and location conditions are suitable, provide an opportunity for farmers to maintain production throughout the year. This project was initiated at the request of the Ministry of Agriculture and Rural Development (MARD) to 1) test the farming system for scaling out; 2) identify risk factors for rice and shrimp production; 3) better understand the benefit of growing rice and shrimp together; and 4) create a basis for developing better management practices. Initially there was a focus on scientifically validating the efficiency of these systems; however, severe drought conditions caused recurrent rice crop losses and impacted on the research at Hoa My Commune in Ca Mau where farmers faced the challenges of severe salinity and acid sulfate soils. This led to more in-depth research on the risk factors for rice and shrimp production. A review of the project recommended that the project should be extended to include research activities at study sites that were less impacted by severe drought. The project extension enabled the team to conduct field trials on system processes, farming risk factors and testing better management practices. Tan Bang Commune was selected as a second site. Site characterisation and risk factors for rice and shrimp production where evaluated along with data collection at Hoa My Commune for comparative purposes. Based on the findings of the risk factor studies, and the outputs of a scientific and expert (farmer) Bayesian Belief Network (BBN), a series of salt-tolerant rice trials were conducted, better farming practices were tested for rice and to a lesser extent shrimp, and shrimp health was evaluated and linked to farm conditions to create a knowledge platform for future research. The trials identified suitable salt-tolerant rice varieties, demonstrated that sludge from shrimp farming could be used to replace fertiliser for the rice crop, and rice platform conditions could be improved by tilling, washing and leaching of the residual salt and modifying the rice growing platform. The project also made recommendations on the timing of sowing to address salinity issues that affect the early stages of rice growth. These practices reduce the need for fertiliser, have improved rice yields, and increased the profitability of rice-shrimp farming system. The study found that natural food production is low for shrimp due to water quality conditions that do not enable the conversion of nitrogen to natural food. Shrimp are also stressed by low dissolved oxygen concentrations and, periodically, by salinity and water temperatures outside their optimal range for growth and to maintain health. Further research is needed to test better management practices for shrimp nutrition and methods to increase dissolved oxygen concentrations and temperature conditions. Pilot trials demonstrated that shrimp yields could be improved e.g. supplementary feed can increase the value of the shrimp crop by USD 1500 annually. The project was led by the University of New South Wales and the Research Institute for Aquaculture 2 (RIA2), and involved Can Tho University (CTU), Griffith University, Charles Sturt University (CSU), the Cuu Long Rice Research Institute (CLRRI) and the Department of Agriculture and Rural Development (DARD) in collaboration with farmers from Hoa My and Tang Bang Communes in Ca Mau, Vietnam. Farmers from Kien Giang and Bac Lieu also contributed to the development of the BBN that framed the research. Final report: Improving the sustainability of rice-shrimp farming systems in the Mekong Delta, Vietnam Page 7 3 Background The Mekong Delta is the most important rice-producing region in Vietnam and accounts for more than 50 of annual rice production (General Statistics Office, Vietnam, 2012). Approximately 70 of agricultural land in the Mekong Delta is under rice cultivation, but in areas influenced by dry season salinity, rice farming is restricted to the wet season when the salinity of canal and other surface waters is sufficiently low for the available rice varieties. In recent years, rice farming in the wet season has resulted in regular crop losses attributed to elevated salinity associated with high evaporation rates, modified canal networks, changes in how tidal gates are operated, expansion of brackishwater aquaculture, lower rainfall and shorter wet seasons (Nhan et al. 2007, 2011). Farmers are also changing water management practices to extend the shrimp growing season leading to longer periods of soil and water salinity that then impacts the rice growing season. Shrimp is the most valuable commodity for the region and accounts for 42 of the country’s earnings from seafood production. Approximately 76 of Vietnam’s shrimp production occurs in the Mekong Delta. The Government of Vietnam advocated (Resolution No. 09NQ-CP) the conversion of unproductive agricultural land to higher value shrimp production systems. In the last few decades, integrated rice-shrimp farming has been promoted to minimise the crop failure risks associated with a rice monoculture system, and the need to maintain rice production levels but offer farmers an additional crop (shrimp) for income (Preston and Clayton 2003). Rice-shrimp farming is now widely adopted by former rice farmers, particularly in parts of the Mekong where there is seasonal variation in water salinity. Shrimp monoculture is restricted to areas close to the coastline where marine water intrusion is sufficiently high year-round to ensure shrimp are not stressed by low salinity. A key feature of rice-shrimp farming systems is that they are commonly operated by families rather than commercial enterprises and involve low stocking densities and low-cost farm inputs. However, despite the reduced risks to crops due to the low-intensity farming systems, there are still issues; profitability has been low and production failures still occur. This is due to factors such as rainfall variability, modifications of the canal networks and increasing pressure on water resources. Flooding, drought and unpredictable variations in water salinity are significant risk factors for rice and shrimp. Therefore, rice-shrimp systems have become increasingly difficult to manage, leading to environmental and livelihood impacts. Recent research has identified new salt-tolerant rice varieties that have the potential to be used on farms affected by residual salt from shrimp production in the dry season (CLRRI, unpublished data). Additionally, a project funded by the Ministry of Agriculture and Rural Development (MARD), and coordinated by RIA2, designed new rice-shrimp farming systems to a preliminary stage which were then tested by this project. In a 2010 ACIAR Country Consultation process, the Government of Vietnam identified a need for research on the risk factors for rice-shrimp farming systems, the benefits of farming rice and shrimp in an integrated system, testing of the new farming systems and modification of pond and canal designs to manage constraints and improve both rice and shrimp yields. To date, there has been a lack of scientific investigation into risk factors for this farming system, particularly environmental constraints and ways to manage them. An understanding of the underlying processes and mechanisms was urgently needed to develop appropriate management strategies and to enable farmers to respond to increasing wet-season salinity. The benefits of farming the two crops in the same system was, prior to this research, anecdotal with a paucity of research on processes that, if understood, could enable more efficient farming and determine the influence of one crop on the productivity of the other. The main aim of the project was to scientifically test the efficiency of the system and to more specifically identify and describe risk factors for poor production, to study the movement of Final report: Improving the sustainability of rice-shrimp farming systems in the Mekong Delta, Vietnam Page 8 nutrients and evaluate the benefits of farming rice and shrimp in the same system as a basis for improving the crop yields and reducing farming costs. The study commenced in 2013 in Ca Mau and involved capacity building, studies on soil and water quality, assessment of nutrient dynamics and growth performance of rice and shrimp, and eventually developing better management practices for rice that were assessed over several rice growing seasons. Trials on better management practices for shrimp were also undertaken following a comprehensive study of environmental factors identified key water quality variables that affected shrimp health and nutrition. The main outputs of the project include scientific knowledge on pondrice platform processes, a better skilled research team with expertise in evaluating soil, water, rice and shrimp interactions, scientific publications on risk factors for rice and shrimp production, a publication on better management practices for rice farming, extension materials for technical and extension officers, and guidelines for farmers. The project also captured and analysed socio-economic data on rice-farming systems, built strong partnerships between scientists, extension and technical officers and farmers, and facilitated partnerships and information exchange between farmers and farmer groups. Figure 1: Rice-shrimp farming system showing the raised rice platform and surrounding ditch where shrimp and crabs are farmed. Source: J.Sammut, UNSW Final report: Improving the sustainability of rice-shrimp farming systems in the Mekong Delta, Vietnam Page 9 4 Objectives The overall objective was to understand the mechanisms, processes and functionality of rice–shrimp farming systems through rigorous scientific investigations in order to achieve sustainable production. The specific objectives were: 1. To better understand the key components of the sustainability of rice-shrimp farming systems; 2. To determine the sustainability of the rice-shrimp farming system by testing the identified key risk factors and system components; 3. To determine, explain and quantify the benefits to productivity of integrating rice and shrimp farming; and 4. To identify and promote better management strategies to improve productivity and sustainability of rice-shrimp farming systems. Figure 2: Over 20 salt-tolerant rice varieties were tested at Tang Bang Commune. Several strains were selected for further trials and higher yields were achieved. Photo: J.Sammut (UNSW) Final report: Improving the sustainability of rice-shrimp farming systems in the Mekong Delta, Vietnam Page 10 5 Methodology Objective 1: To better understand the key components of the sustainability of rice- shrimp farming systems 1.1 Compile existing information held by researcherspublications Information was sourced from peer-reviewed publications and government and non- government agency reports, and a comprehensive literature review completed. The findings of publications in Vietnamese were translated into English by RIA2 staff. Content of some materials was analysed using NVivo software to identify common themes. The resulting literature review will be revised to incorporate findings from the project and new knowledge from other research; a final review will incorporate findings from the literature review and project-based research to produce a manuscript on the status, challenges and management of rice-shrimp farming that will be submitted to a scientific journal. 1. 2 Conduct research focus group workshops to develop an initial BBN Focus group workshops were undertaken over several stages with extension officers and farmers in each region (Ca Mau, Bac Lieu and Kien Giang). Groups of experts were formed to capture knowledge and experience critical to understanding the key aspects of the rice- shrimp farming system. These workshops occurred over three research trips in October 2013, July 2014 and November 2015. The main output of these workshops was the development of the BBN. We followed an iterative process of validation at each stage of the workshops to ensure specific regional biases did not affect the outcomes, and to ensure the BBN reflected the knowledge and experience of these participants. The entire process began with a one-day introductory training workshop for facilitators from RIA2, CTU, CLRRI, who worked with the BBN developers to interact with the farmers and policy officers as facilitators and translators. The preliminary training workshop focused on the theory and application of BBNs and culminated in groups of researchers developing and presenting their own BBN for scrutiny by other workshop participants. This process ensured the training worked in two directions - the newly trained facilitators had a clear understanding of the BBN development process from beginning to end, and the BBN trainers and modellers were introduced to important environmental and agricultural processes, as perceived by the facilitators. Understanding the processes that were viewed as important by the facilitators also helped identify possible biases they may have unconsciously focused on in the subsequent expert elicitation workshops. Given the language barrier between the modellers and the experts, these biases may have otherwise been missed. Following the training workshop and an initial research trip, a core group of facilitators from RIA2, CTU and CLRRI worked closely with the BBN developers to produce the prototype BBN. While the final BBN was not completed until early in 2016, the initial focus groups held in October 2013 and July 2014 identified key insights and factors that affect the sustainability of rice-shrimp farming systems. From these workshops, we were able to develop and modify key components of research on the farms. 1.3 Conduct training in BBN development We conducted four formal training sessions in BBN development over the life of the project, involving team members from RIA2, CTU and CLRRI. The training sessions are summarised in Table 1. Informal training was also provided to the team. Final report: Improving the sustainability of rice-shrimp farming systems in the Mekong Delta, Vietnam Page 11 Table 1: Summary of formal BBN training sessions Location Date Title Attendees RIA2 Sub- station Ca Mau October 2013 Introduction to BBNs All team members who attended project inception, approx 25. RIA2 – Ho Chi Minh City July 2014 Bayesian Belief Networks for agricultural decision making Five team members including 3 staff from RIA2, 1 staff from CTU and 1 student from GU. CTU – Can Tho February 2018 Using Bayesian Belief Networks as a tool for making agricultural and environmental decisions 13 participants including 3 staff from CTU, 2 staff from CLRRI and 9 students from CTU. RIA2 Ho Chi Minh City November 2019 Using Bayesian Belief Networks as a tool for making agricultural and environmental decisions 5 participants who were all staff from RIA2 Objective 2: To determine the sustainability of the rice-shrimp farming system by testing the identified key risk factors and system components 2.1a Test the influence of key factors that will affect nutrient availability and rice yield Soil surveys were conducted at both field sites (Hoa My and Tan Bang Communes) on farms involved in the project activities (n=18 and n=6, respectively). Profile descriptions, including chemical analysis for soil horizons, were recorded. Soil characteristics were examined to ascertain possible limitations to rice production. As salinity was ranked as the greatest risk factor during the BBN development phase, the salinity of canal water and field water was recorded at all farms throughout the rice and shrimp production seasons. The relationship between surface water salinity and soil solution salinity was studied on a subset of farms at Hoa My Commune. This work demonstrated that soil solution salinity was a more useful metric for temporal studies relating to plant production. Consequently, soil solution salinity was included in basic measures at study sites, including Tan Bang. The influence of salinity on rice production was studied in glasshouse trials and in the field. Rice variety trials were conducted at Hoa My and Tan Bang to test short duration, salt tolerant varieties against long duration traditional varieties. At Tan Bang successful varieties were short listed following a field trial (n=16) in 2017 for time of sowing (n=3) trials in 2018. 2.1b Quantify the improvement to rice production possible by platform preparation Research conducted in years 1 to 3 at Hoa My identified salinity as the key limitation to rice production rather than nutrition. Prolonging the shrimp season, along with the conditions of drought at the end of the shrimp season, elevated salinity of the soil solution and ponded water. This caused a delay in establishing the crop, death of seedlings and plant stress at the start of season, and termination of grain formation at the onset of the dry season. Final report: Improving the sustainability of rice-shrimp farming systems in the Mekong Delta, Vietnam Page 12 Greenhouse and lab trials indicated that removal of salt could be enhanced by facilitating leaching rather than the current farmer practice of horizontal washing (dilution) on the soil platform. Pot trials conducted at CTU, CLRRI and CSU examined the efficiency of decreasing soil solution salinity by soil management (liming, tillage) and water management (washing and manipulating water height). These findings were validated in field trials at Hoa My (tillage, water height management) and at Tan Bang (tillage and liming, improved drainage). Time of platform preparation was also studied in the field at Tan Bang in conjunction with time of sowing trials. The method of sowing of rice was also tested in the field. At Hoa My commune, rice was either transplanted or directly sown on different farms. At Tan Bang, the farmers had begun to experiment with throwing seedlings onto the water covered rice platforms. This method was thought to provide the seedlings with more time in the less saline surface soil than transplanted seedlings that are pushed into the soil that may be saline below the surface. Field experiments were conducted to test the influence on rice yield of these two methods. Platform preparation has also been shown to be compromised when shrimp are also grown in the wet season with rice. Even so, platform preparation remains a response sensitive management activity for farmers. Research in year 45, under the project extension, trialed low-cost management options for farmers at the Tan Bang site where only rice is grown in the wet season. Utilization of pond sludge generated from a shrimp crop as fertilizer in accordance with applying enhanced salinity washing techniques at the early wet season is promising to bring higher certainty for the rice crop, and as a consequence, sustain the integrated system of rice and shrimp. Farmers, researchers and DARD considered this a key research activity that required refinement under field conditions at Tan Bang. The potential transferability of this work should provide substantial benefits to large areas of the Vietnamese Mekong Delta at a time of predicted increases in salinization. 2.2 Quantify the fertiliser replacement value of shrimp pond sludge in rice cultivation Shrimp pond sludge accumulates during the shrimp production phase because of waste from feed (when used – often not), faeces, algal production and accumulation of dead diatoms. Sludge can be used as a source of onsite fertiliser that supplements mineral fertiliser used in the rice production phase. At both Hoa My and Tan Bang, sludge was collected and quantified from a number of ponds to determine the chemical composition (e.g. available and total organic carbon, N, P, K, S, and salinity) of sludge within the system. Two methods of sludge collection were tested; direct collection or in-situ sludge traps at Hoa My. Incubation experiments were carried out in the lab at CTU to examine N and P mineralisation from sludge from various locations within the field. Field trials, utilising micro- plots, were conducted in the rice crop to determine the fertiliser replacement value of sludge on selected farms. In Hoa My, field trials were continuously conducted in years 2014 and 2015, and we tested sludge use as full or partial replacement of inorganic fertiliser at full or fractional recommended rates. Experiments conducted at Hoa My in Year 1 of the project demonstrated that decreased fertiliser use might result in economic savings without any deleterious effect on rice yield in saline compromised environments. Severe drought and salinity caused trial failure in Year 2. As such, further field validation was required before results could be extended with confidence. DARD required at least two crop cycles before considering a modified practice thus trials were moved to Tan Bang Commune where conditions were more amenable to experimental work and more representative of the conditions faced by farmers across the rice-shrimp farming areas of the Mekong Delta. The same trial was thus repeated at Tan Bang in 2016 and 2017. The results from the repeated field trials demonstrated that sludge could fully replace chemical fertilizers applied as farmer’s practice, even higher grain yield could be gained as supplying sludge combined with fractional amount of chemical fertilisers. Final report: Improving the sustainability of rice-shrimp farming systems in the Mekong Delta, Vietnam Page 13 The outcomes of these trials informed the soil management component of the BBN. As for all activities, economic data were collected to feed information into the Economic BBN and to demonstrate costs to farmers and extension officers. 2.3 Train staff in laboratory and field research techniques The Australian project staff trained research and technical staff in Vietnam partner agencies building their skills in soil and water assessment, the use of isotopic tracers, live food classification and other laboratory and field methods. A training needs assessment was undertaken in Year 1 to ensure that research and technical staff would be trained in relevant skills areas before research activities were implemented. The training program also built research and technical capacity that will continue beyond the life of the project. Staff of RIA2, CLRRI and CTU participated in the training, and one CTU team member was trained in nuclear techniques (Isotopic and elemental profiling) at UNSW and ANSTO. Moreover, staff were also trained in data analysis and reportpaper writing in both languages. Farmers were trained to check water quality and shrimp health on-site, evaluate results and to collected shrimp and rice samples for analysis. Research students in Vietnam and Australia were engaged in projects aligned with the research of the project. Six UNSW interns were also hosted by RIA2, CTU and CLRRI; the interns participated in field work, surveys and focus group discussions. There was one PhD student from CTU working on analyses of nutritional values of sludge and determination of rice’s N use efficiency from sludge in comparison to that from chemical N fertilizer. He successfully passed the internal defense round and is expected to present his dissertation in late 2020. Objective 3: To determine, explain and quantify the benefits to productivity of integrating rice and shrimp farming Detailed investigation of nutrient processes within the traditional rice–shrimp system and comparison with the new designs were conducted. This involved determining nutrient balances and using isotopic tracers to determine dominant inputs and outputs to explore linkages between rice and shrimp crops. These studies allowed the benefits of rice to shrimp farming and vice versa to be evaluated, as well as identifying where the current system is unsustainable and could be improved. 3.1 Determine nutrient (carbon, nitrogen, phosphorus) balance and of the rice–shrimp system in traditional and improved systems Six traditional and six each of the improved pond designs were used in Cai Nuoc district (Hoa My Commune), Ca Mau Province, to determine carbon, nitrogen and phosphorus budgets for both the rice and shrimp cycles over one year. The total volumes of water in ponds, water exchange, nutrient concentrations in the water (including dissolved nutrients such as ammonium), and sediment biomass of particulate matter in the water column, the platform and stubble were determined. These data were important to refining soil leachingsoil washing methods to prepare rice platforms and underpinned trials at Tan Bang under the project extension. Additionally, rice and shrimp seed stock and harvest biomasses, and foodfertilizer inputs were assessed. This involved regular visits to ponds by researchers to undertake sampling and collate information from farmers. Whole-season, whole-pond nutrient and carbon budgets were constructed for both current and improved systems. 3.2 Quantify temporal water and soil quality parameters throughout current and improved rice–shrimp systems Temporal changes in water and soil quality parameters were measured in the same ponds used for the nutrient balance estimates (Activity 3.1). This included assessment of the effectiveness of reservoirs in the MARD system to buffer high salinity during the rice production season. Water and soil samples were collected from the rice platform, Final report: Improving the sustainability of rice-shrimp farming systems in the Mekong Delta, Vietnam Page 14 surrounding trench, dyke walls, and associated nursery pond (improved farm design) to determine their specific influence on pond environment. This included samples for pesticide analysis by RIA2 and shrimp health assessment. Systematic or fixed interval sampling was used, but the frequency of sampling was increased during a change in farm practice, increased rainfall or other acute events. The number of samples and key variables were determined by the design of field experiments. The key soil and water variables were measured to describe spatial and temporal variations during the production cycles. This activity provided data for Activities 2.1, 3.1 and 3.3. Physical and chemical properties were determined using standard in situ and laboratory methods. Where possible, data loggers were used for basic variables such as water temperature, water depth, dissolved oxygen, pH, EC and turbidity. Additionally, soil parameters were measured including but not limited to REDOX, pH, EC, iron, aluminium, hydrogen sulfide. Regular, fixed interval, in situ spot measurements were also collected at logged sites as a backup. Water depth was identified as a factor likely to affect food availability for shrimp. Water depth affects the water temperature on the platform, which in turn affects the likelihood of shrimp accessing the platform during the hot hours of the day. Additionally, water depth affects the scale of epiphyte growth on the rice stubble. Epiphytes and benthic algae provide a potentially important source of food for shrimp. Key parameters were measured in situ to determine the availability of the platform for shrimp, and the amount and quality of food available on the platform. This was done in the same ponds as those used for nutrient balance studies (Activity 3.1). Access points were built on a number of ponds for sampling and measurements on the platform. Temperature loggers were deployed onto platforms to measure temperature and water depth. Epiphyte biomass and nutritional composition were measured by sampling rice stubble structures and harvesting the epiphytes per plant, and benthic algal biomass, throughout shrimp grow-out seasons. In years 3 and 4, sampling was undertaken in Tan Bang district, Ca Mau province in three farms to measure and analyse the same parameters outlined above. 3.3 Determine the contribution of an annual rice production cycle to production of shrimp, and vice versa, within the rice–shrimp system A pilot study was undertaken to determine variability in key measures related to nutrient cycling within platforms and between ponds; this was conducted during the first year of shrimp culture when the carbon, nitrogen and phosphorus budgets were determined for the shrimp cycle. This involved sampling multiple quadrats for epiphyte, benthic algae and rice stubble biomass, and soil samples for nutrients at each site. This set the foundation for the spatial intensity of sampling required to capture the variability across platforms in the next shrimp season, when the labeling studies were done. The contribution of rice crops to shrimp production was examined in the second year. This involved using infield microplots allowing the spiking of rice with 15 N-labelled urea fertiliser and allowing the incorporation of the signal into the plant. After harvesting, the15 N values in the rice and stubble were determined, giving a measure of the efficiency of fertiliser to the rice crop. Importantly, the 15 N in the labeled stubble was then traced through the food chain to the epiphytes within those microplots. In a separate15 N labeled field study, run parallel to the microplot trial, 15 N was added to the water and by sampling epiphytes and shrimp, the transfer of 15 N from epiphytes and benthic algae on the platforms to the shrimp was determined. This combined experiment was undertaken in a trial phase in the first year, then refined and repeated in the second year. The data were used to quantify the contribution of nitrogen from the rice crop cycle to the shrimp production. During Years 1 to 3, rice crop failures at Hoa My Commune, due to excessive salinity, did not allow the contributions of rice production to the shrimp production component to be examined. The establishment of the Tan Bang study location enabled the research team to collect data from reliable rice crops and this enabled the broader influence of rice on shrimp Final report: Improving the sustainability of rice-shrimp farming systems in the Mekong Delta, Vietnam Page 15 production to be determined. Research in year 45 (under an extension) included field experiments conducted with and without rice establishment to determine the effects of rice on soil quality and associated nutritional dynamics influencing the following shrimp production season. At the end of the rice crop, rice stubble was also sampled to estimate the amount of rice residue remained in experimental plots. The effects of pond sludge on the rice performance, which in turn affects the shrimp health and production in the following season, were also validated in the extension phase at the new location. Sludge addition combined with rice or without rice experimental treatments was designed at large scale in-situ. At harvest, grain was collected separately to measure the rice yields, whereas rice plant biomass and stubble were used to determine the effects of the rice planting and rice residue on the variation of soil and water chemical variables impacting on the following shrimp growth and production. The production of hydrogen sulfide from contrasting pond sediments was studied in lab column studies. Hydrogen sulfide volume produced and the resultant concentration in the head water was reported during the incubation study. This objective was also combined with Objective 3.5; see methods below. 3.4 Develop a growth model for shrimp in rice-shrimp ponds In the first two years of the project, at Hoa My Commune, farmers grew shrimp throughout the shrimp season and into the rice season. Survival in all rice-shrimp ponds was poor,